There's a lot to talk about. I am in chase mode right now debating the PNW, Tetons, Utah, and northern Colorado, or perhaps I grab 3 of the 4?  The PNW will get slammed in a big way Saturday night with several feet of much-needed snow. This is a classic storm that comes in with 3,500 snow levels (Warm and wet) and finishes at 500 feet. Mt Baker will see the initial brunt of the storm totals Saturday night into Sunday (8-16) with strong SW winds (Red flags: Wind impacted in spots initially Saturday night, Sunday powder crowds, 1st deep storm of the season- could be epic or a waiting game). 

Snow will fall heavily into Sunday, especially further south towards Stevens, Alpental, (East side of the Cascade Range grabs 5-10), and eventually through southern Washington and most of the Cascade Range of Oregon. Puget Sound Convergence Zones (PSCZ) will form early Sunday as winds veer to the W, NW allowing cold air to converge from the north and south (Split flow) over King and Snohomish Counties (Snoqualmie, Stevens). PSCZ is essentially Northwest winds in the upper atmosphere that become split by the Olympic Mountains, then re-converge over Puget Sound, causing updrafts and intense snowfall at times. 

Below: Illustration of the PSCZ with split north and south flow merging over the Central Cascades of Washington. 

Through Sunday night I would expect 14-24 inches in many areas of central Washington with 9-14 further south (Crystal- White Pass). Snow begins in earnest over Oregon by daybreak Sunday and continues into Monday (12-18 for the northern OR Cascades with perhaps 8-14 further south towards Bachelor. Bottom Line PNW: Great storm, windy initially with SW flow Saturday night, PSCZ will nail the central WA Cascades, Ride powder from north to south starting Sunday morning and finishing in Oregon late Sunday or early Monday. 

Northern Idaho  (Schweitzer) will see 6-10 inches by late Sunday dropping into the central panhandle near Lookout Pass and most of northern Montana (Might favor GNP or far NW Montana). 

Below: National blended models showing widespread areas of 2-3 feet for the Cascade range through Monday. 

Rockies chases?  

Light snow is trickling down into Montana, Wyoming, UT, and Colorado on Saturday (Appetizer of 2-4 inches). The deep trough over the PNW will likely favor the Tetons for Monday morning or the northern and central Wasatch of Utah Monday-Tuesday. There are some discrepancies on how far south this digs into Utah. I have confidence in Wyoming for grabbing an inch of water by Monday morning. The northern Wasatch range could be favored with SW flow (Snowbasin), and even Park City can deal well with this pattern. Post NW flow could add to snow totals in the Cottonwoods for Tuesday morning.  Bottom Line MT/WY/CO: High confidence for a foot or more for the Tetons, moderate confidence for 10-15 inches for the areas of north-central Utah (Wider spread due to the model divergence). Southern Montana will see lower amounts (3-7). Timing: Early Monday for Montana and Wyoming, Late AM Monday through early Tuesday for the Wasatch Range. 

Below: Sharp cold front approaches Montana by late Sunday and Wyoming early Monday before spreading over Utah and Colorado Monday/Tuesday. This will increase snow ratios (Water to snow) and quality. Strong winds initially might create some drifting or light-density funk in some areas. 

Below: Teton Pass OpenSnow ensembles are pretty confident (Tight lines) for an inch of water by Monday morning (12 inches with good upside potential due to snow ratios). You can see the additional storm by Thursday or Friday increasing these totals. 

Below: lower confidence on snow totals for Brighton Ski area with wider lines (GFS-Red- Euro- Blue) indicating anywhere from 1/2 to 1 inch of water through Monday night. This system begins Monday morning, peaking Monday afternoon to evening (Monday PM or Tuesday AM powder). Utah will grab decent totals but the spread and confidence are a bit lower (8-16). WIder spread of totals based on these ensembles. 

Below: Snowfall totals at Alta from storms Saturday-Tuesday and again late this week. This is based on the GFS which is bullish for 2-foot storm totals through the end of the week. It's likely that 12-15 land for Monday/Tuesday however there are some ensemble uncertainties noted above so amounts might be a bit lower initially. 

For Colorado, this storm will impact most ski areas with the heaviest totals likely in the Elk (Aspen), Gunnison (Crested Butte), and extending north to Rout County (Steamboat/Rabbit Ears).  These areas could grab 9-15 inches of snow with a bit more confidence from Aspen to Steamboat. However, the models show 5-10 inches elsewhere along the I-70 Corridor with the European starting to hint towards deep snow for Grand County (Winter Park, RNP in Boulder County) with post-northerly winds (good for the Divide). It's a wide range of .6 inches of water to just over an inch. NW winds along the western corridor could bring some upside to Vail Pass, and even Breckenridge in Summit County.  With low temps, and high snow ratios this could be a blockbuster storm for some areas. Peak snowfall will be from Late Monday night through Tuesday evening. Ride late Monday or early Tuesday.  Even the southern area from Telluride to Wolf Creek will see moderate snow primarily from Tuesday to Wednesday.  Bottom Line: Ride Colorado on Tuesday morning with good timing for freshies anywhere from 7-16 inches (The highest confidence is from Steamboat to Snowmass, the I-70 corridor is a solid wildcard, and even Grand County where winds may shift to the north). This is a decent storm. 

Below: Total Precipitation through late Sunday night (Day 7) which will change that far out! The takeaway is significant moisture is likely for the west, especially the PNW, western BC, Sierra (Wildcard for the late week), and many areas of the Rockies. High confidence in the pattern, with a bit lower confidence in these totals since some of this, will occur late next week. 

This will be brief (I am tapped out on the short-term forecast).  Another good snow producer moves into the PNW by mid-next week. This system will bring another deep storm to the PNW, and push south over the Sierra (Remember last week the models flip-flopped so don't get too excited yet). I have decent confidence at this point. The European and GFS disagree on far south the low will slide. The big differences are below. 

Below: The GFS (American model) is showing a decent storm for the Sierra by late next week (12-20).

Below: Is the euro on steroids?  Usually, it's the GFS). This is showing several feet for the Sierra range by late Friday night!  let's hope it happens. WOW. 

It's too far out to forecast with accuracy, however, it's highly likely that late next week sees additional snow for the Rockies as the low pushes moisture north into many regions. Some models show some decent amounts stacking up again for the Rockies. 

We might stay unsettled into the December 4-6th timeframe as well. 

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See you on the first chair! 

Powderchaser Steve